That’s Yoko Ono’s advice to Sir Paul McCartney, who is keen to change the song writing credits on songs he primarily composed. He recently released an album of songs performed during a 2002 US concert tour, and on 20 of the 36 songs he transposed the credit line to “Paul McCartney and John Lennon” from the well-known “Lennon-McCartney.”
The full list of songs so changed, as well as more background info, including details of Yoko’s advice, are available here.